Introduction to LIGO & Gravitational Waves

Sources of Gravitational Waves

In general, any acceleration that is not spherically
or cylindrically symmetric will produce a gravitational wave.
Consider a star that goes supernova. This explosion will produce
gravitational waves if the mass is not ejected in a spherically
symmetric way, although the center of mass may be in the same position
before and after the explosion. Another example is a spinning
star. A perfectly spherical star will not produce a gravitational wave,
but a lumpy star will.

The gravitational waves that modern detectors
are sensitive to would be in the audible frequency range
if they were sound waves. In that sense, these detectors can be
thought of as ‘gravitational wave radios.’ Just like radio waves
cannot be heard without a radio to detect the radio waves and decode
the music signal to send to the speakers, gravitational waves cannot be
heard without a detector to distinguish the gravitational wave and send
that signal to speakers. All of the physics that went into the
production of a gravitational wave is then encoded in this ‘music’ for
physicists to decode. In the following descriptions of
gravitational waves, the ‘sound’ they make will often be described to
illustrate the properties of the expected signal.